Highlight on New Mexico: Department of Health Warns of Plague Activity

On May 23, 2014, the New Mexico Department of Health (NMDOH) warned of significant plague activity in the East Mountain area of the state, which includes Bernalillo, Torrance, and Santa Fe counties. In April, the NMDOH reported that a 57-year-old Torrance County man had contracted plague and was hospitalized for over a month. This was the first human case of plague in New Mexico in 2014. NMDOH expects the man to recover. NMDOH also reported that three dogs from the Edgewood area of Santa Fe County and one cat from Torrance County have confirmed plague.

With regard to the Torrance County man, NMDOH Secretary Retta Ward, MPH stated that “An epidemiologic investigation and an environmental investigation around the home of the plague case are being conducted by NMDOH staff to look for ongoing risk and to ensure the safety of the immediate family and neighbors. Staff will go door to door to neighbors near the case to inform them about plague found in the area and educate them on reducing their risk. Health care providers and others close to the patient who have been determined to have been exposed are taking preventive antibiotic therapy.” Antibiotics are currently used to treat plague. The National Institute of Allergy and Infectious Diseases is also working with the U.S. Department of Defense, the Centers for Disease Control and Prevention (CDC), and the U.S. Department of Energy to develop a vaccine that protects against inhalationally acquired pneumonic plague. According to the CDC, while plague vaccines are in development, they are not expected to be commercially available in the immediate future.

It is important to note that a rise in plague cases at this time of year is not unusual. According to the CDC, while plague cases can occur in any season of the year, most cases occur from late Spring to early Autumn. In addition, Dr. Paul Ettestad, public health veterinarian for the NMDOH reports that “Plague cases have occurred every month of the year in New Mexico, but most cases usually occur in the summer months.” According to Dr. Ettestad, “It is especially important now that it is warming up to take precautions to avoid rodents and their fleas which can expose you to plague. Pets that are allowed to roam and hunt can bring infected fleas from dead rodents back into the home, putting you and your children at risk.”

The CDC has determined that plague is most common in the rural and semi-rural areas of the following two regions: (1) New Mexico, northern Arizona, and southern Colorado; and (2) California, southern Oregon, and far western Nevada. The NMDOH reports that in New Mexico there were four human plague cases in 2013 with one fatality, one human plague case in 2012, two human cases of plague in 2011, no cases in 2010, and six human cases of plague in 2009, one of them fatal.

The CDC reports that plague is caused by the Yersinia pestis bacteria, which affects rodents, certain other animals and humans. The CDC believes that humans become infected with plague in one of three ways: (1) when they are bitten by a flea that is infected with the plague bacteria; (2) from direct contact with infected tissues or fluids of a animal that is sick or has died from the plague; and (3) by inhaling respiratory droplets after close contact with cats and humans with the pneumonic form of plague. The most common form of transmission, however, is believed to be by flea bite. The CDC identifies and describes the three forms of plague as follows:

Bubonic. Patients develop sudden onset of fever, headache, chills, and weakness and one or more swollen, tender and painful lymph nodes. This form is usually the result of an infected flea bite. The bacteria multiply in the lymph node closest to where the bacteria entered the human body. If the patient is not treated with appropriate antibiotics, the bacteria can spread to other parts of the body. The incubation period for bubonic plague is two to six days after exposure.

Septic. Patients develop fever, chills, extreme weakness, abdominal pain, shock, and possibly bleeding into the skin and other organs. Skin and other tissues may turn black and die, especially on fingers, toes, and the nose. Septicemic plague can occur as the first symptoms of plague, or may develop from untreated bubonic plague. This form results from bites of infected fleas or from handling an infected animal.

Pneumonic. Patients develop fever, headache, weakness, and a rapidly developing pneumonia with shortness of breath, chest pain, cough, and sometimes bloody or watery mucous. Pneumonic plague may develop from inhaling infectious droplets or from untreated bubonic or septicemic plague that spreads to the lungs. The pneumonia may cause respiratory failure and shock. Pneumonic plague is the most serious form of the disease and is the only form of plague that can be spread from person to person. The incubation period for a person infected by inhaling infectious droplets is one to three days.

The CDC reports that the mortality rate from the plague during the pre-antibiotic era (1900-1941) was 66 percent in the United States. By 1999-2010, antibiotics had reduced the overall mortality rate to 11 percent. The CDC recommends beginning antibiotic therapy as soon as plague is suspected. The drugs of choice are streptomycin or gentamicin, but tetracyclines, fluoroquinolones and chloramphenicol are also effective.

The NMDOH makes the following recommendations to prevent plague: (1) avoid sick or dead rodents and rabbits, and their nests and burrows; (2) keep your pets from roaming and hunting; (3) talk to your veterinarian about using an appropriate flea control product on your pets as not all products are safe for cats, dogs, or your children; (4) clean up areas near the house where rodents could live, such as woodpiles, brush piles, junk and abandoned vehicles; (5) sick pets should be examined promptly by a veterinarian; (6) see your doctor about any unexplained illness involving a sudden and severe fever; (7) put hay, wood, and compost piles as far as possible from your home; and (8) don’t leave your pet’s food and water where mice can get to it.

In addition to the NMDOH recommendations, the CDC also advises: (1) report sick or dead animals to the local health department or law enforcement officials; (2) do not let pets sleep in bed with you; and (3) use insect repellent that contains DEET to prevent fleas bites.